In ophthalmic microsurgery, such as lens removal, instruments are used with either horizontal or axial oscillatory movements. High frequency rotary (angular) oscillation to achieve lens destruction is not presently available. Furthermore, conventional horizontal or axial oscillatory instruments employing piezoelectric technology tend to create heat during operation which can damage ocular tissues. The very high frequency of these conventional oscillatory surgical instruments also can cause indirect damage to adjacent ocular tissues.
Therefore, what has been needed in this art is relatively low frequency rotary oscillatory coupling which would then be especially adapted for use with surgical instruments, particularly instruments employed in ophthalmic microsurgery. It is towards providing such a need that the present invention is directed.
Broadly, the present invention relates to a rotary oscillatory coupling and method of imparting rotary oscillatory movement by means of repetitive rotational direction reversals caused by the interactive influence of respective magnetic fields of positionally opposed permanent magnets. More specifically, the coupling of this invention includes a pair of independently rotatable hubs which carry paired permanent magnets of either opposite or like poles. One of the hubs is continuously rotated so that the magnetic field of the magnet it carries will cooperatively interact with the magnetic field of the magnet carried by the other hub and thereby cause the other hub to rotate. The other hub is, however, prevented from rotating a complete turn which thereby causes rotation direction reversal. Upon coming under the influence of the magnet in the continuously rotated hub, therefore, the other hub will again reverse its rotation direction. In such a manner, oscillatory rotary motion is imparted to the other hub.
In particularly preferred forms, the invention is embodied in an assembly for coupling a motor to a surgical instrument (e.g., for ophthalmic microsurgery such as lens removal) so as to achieve high frequency rotary (angular) oscillation. The coupling includes a pair of opposed hubs which are independently rotatable about a common axis. At least one pair of magnets is provided in the opposed faces of the hubs. The proximal hub is continuously rotated in a selected rotational direction by means of a suitable motor.
During a portion of the proximal hub's rotation, the distal hub will concurrently be rotated under influence of the magnetic field of the permanent magnet located in the proximal hub. The distal hub is, however, prevented from rotating a complete cycle by virtue of a mechanical stop. Upon encountering the mechanical stop, the distal hub will become magnetically "uncoupled" (to be defined below) from the leading magnet of the proximal hub thereby causing the distal hub to reverse its rotational direction compared to the proximal hub. When the magnets of the proximal and distal hubs again are positioned such that their respective magnetic fields interact(i.e., magnetically "coupled", to be defined below), the distal hub will again experience another reversal of rotation direction. This functional process repeats itself during subsequent rotational cycles to cause the distal hub to undergo high frequency oscillations.
Further aspects and advantages of this invention will become more clear from the following detailed description of the preferred exemplary embodiments thereof.